Controlling the moisture,mullen and basis weight of paper

ABSTRACT

METHOD AND SYSTEMS FOR CONTROLLING THE MOISTURE CONTENT, THE MULLEN, AND THE BASIS WEIGHT OF A PAPER WHEREBY EACH IS MEASURED AND IF CORRECTIONS ARE REQUIRED, A COMPUTER BY MEANS OF A SERIES OF CONTROLLERS DEVELOPS THE APPROPRIATE CONTROL SIGNAL QUANTITIES FOR ADJUSTING A PAPER MAKING MACHINE SO THAT THE DESIRED MEASUREMENTS ARE APPROXIMATED. INCLUDED ARE MOISTURE, MULLEN, AND BASIS WEIGHT CONTROLLERS, WHICH, RESPECTIVELY, VARY THE STEAM SUPPLY TO A PAPER DRYER, THE ENERGY INPUT PER FIBER SUPPLIED BY A PAPER PULP REFINER, AND THE FIBER FLOW TO A HEAD BOX FOR THE MACHINE. THE CORRECTIONS TO ADAPT THEM FOR USE IN MAKING THE ADJUSTMENTS ARE CONVERTED TO CORRESPONDING CONTROL SIGNAL QUANTITIES AND THEN EMPLOYED TO MAKE THE REQUIRED CORRECTION. BECAUSE OF THE INFLUENCE OF MEASUREMENT CHANGES ON EACH OTHER, COMPENSATIONS ARE MADE IN EACH CORRECTION. ALSO PROVISIONS ARE MADE FOR MONITORING REFINER OPERATION IN AN ALTERNATIVE WAY UPON THE OCCURRENCE OF A CERTAIN CONDITION, SUCH AS A MALFUNCTION, FOR PERIODCALLY CHECKING SOME OF THE MEASUREMENTS TO INSURE AGAINST THE MEASURING MEDIUM&#39;&#39;S DEGENERATION, AND FOR BOTH ADJUSTING MACHINE SPEED AND COMPENSATING FOR CHANGES IN MACHINE SPEED.

g- 29, 1972 F. A. RUMMEL ETAL CONTROLLING THE MOISTURE, MULLEN AND BASIS WEIGHT OF PAPER Filed June 22, 1970 3 Sheets-Sheet 1 l-hvlllll INVEN'TORS Jreo/em'ck .14. gamma! BYf Qz'dzara JSz'ecds Aug.

Filed June 22, 1970 F. A. RUMMEL EFAI.

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CONTROLLING THE MOISTURE, MULLEN AND BASIS WEIGHT OF PAPER Filed June 22, 1970 s Sheets-Sheet I MANUAL MANUAL I ENTRY ENTRY-TO T. I

MOISTURE BASIS WT I SET POINT SET POINT T I 260 2901 s2 1 2 I I I 1 T i I T T I DIGITAL I SCAN FILTER I SCAN SGAN MOISTURE LIMIT I BASIS MOISTURE I CHECKI WEIGHT I I l I l 1 DIGITAL ZQZ DIGITAL I DIGITAL I FILTER 36% I FILTER FILTER I LIMIT I LIMIT LIMIT I CHECK I CHECK I CHECK 104 I Page? I I L I I COMPUTE' 54 COMPUTE DIGITAL I NEW DRY FILTER I STEAM FLOW BASIS WT LIMIT I SET POINT I I CHECK 368 I I cOMPUTE l 275 SEES EE SPEED GORR. l I DRY BASIS TO FIBER FLOW l I WT. SET POINT SETPOINT I 37 L Z% J I r l I l I COMPUTE STE A IIZ I LEJW COMPUTE l gg 'g fi SET POINT I N W I ER CORRECTION Z55 cojzrREcTloN I SET POINT I I I I 5 M v I I I GOMPUTE I 128 13' {08 I 536% I I CHANGE l COMPUTE igIg F I 29 I FIBER vALvE I I FLOW CHANGE I I I, I I L75 I I /'/Z6 [54; I DIGITAL DIGITAL J I FILTER FILTER r I LIMIT LIMIT r", I I CHECK CHECK I j I I JNVENTORS I l l Ifzedem'ck IARwzzmeZ II. I BY; IawMdJs/uezae {Wavg United States Patent Office 3,687,802 Patented Aug. 29, 1972 US. Cl. 162-198 34 Claims ABSTRACT OF THE DISCLOSURE Method and systems for controlling the moisture content, the mullen, and the basis weight of a paper whereby each is measured and if corrections are required, a computer by means of a series of controllers develops the appropriate control signal quantities for adjusting a paper making machine so that the desired measurements are approximated. Included are moisture, mullen, and basis weight controllers, which, respectively, vary the steam supply to a paper dryer, the energy input per fiber supplied by a paper pulp refiner, and the fiber flow to a head box for the machine. The corrections to adapt them for use in making the adjustments are converted to corresponding control signal quantities and then employed to make the required correction. Because of the influence of measurement changes on each other, compensations are made in each correction. Also provisions are made for monitoring refiner operation in an alternative way upon the occurrence of a certain condition, such as a malfunction, for periodically checking some of the measurements to insure against the measuring mediums degeneration, and for both adjusting machine speed and compensating for changes in machine speed.

This invention relates to improvements in method and systems for controlling the moisture, mullen, and basis weight of paper and the like.

The finished paper from a paper making machine must be in accordance with certain moisture content, mullen, and basis weight standards for that particular grade of paper. If there is a variation beyond acceptable limits, a correction must be made. Since the correction of one standard usually involves another; e.g., the mullen is affected by both the moisture content and the basis weight, more than one correction must usually be made. Variations in the speed of the machine will also influence both the basis weight and the moisture content of the paper. Another factor to be considered is system lag. Because of this lag a correction does not result in an instantaneous change in the finished paper; therefore, during this interval of delay, over or under correction based on interim measurements must be avoided.

With the foregoing in mind, novel method and systems the basis weight of paper. A related object is a paper 7 making machine control that monitors the quantity of the drying medium supplied to a paper stock dryer for a predetermined interval and adjusts machine speed in accordance with deviations from a desired quantity.

Further contemplated are novel method and systems for controlling the moisture content of paper made by the paper making machine whereby unique provision is made for utilizing the drying medium as a control variable and also for indirectly compensating for the influence of machine speed variations on the moisture content.

A further objective are unique method and systems for controlling the mullen of paper made by a paper making machine whereby the mullen is controlled by monitoring the energy supplied per stock fiber by the refiners. Other related objects are the provision of novel controls in,- cluding a control for monitoring the refiner supplied energy by measuring the consistency of the paper stock and the temperature change in paper stock as it is refined; a control for an alternate way of monitoring refiner supplied energy upon occurrence of a certain condition; a control for measuring freeness and relating this to the mullen and the refiner supplied energy; a control for periodically checking one or more of the measurements to insure against degeneration of the measuring medium and the measurement from the sensor; a control for individually controlling a plurality of refiners and compensating for any difference in their individual efficiencies; and a control for monitoring refiner supplied energy by measuring the electric power consumed and the freeness and the consistency of the paper stock.

The foregoing and other objects and advantages of the invention will become apparent from the following description and the accompanying drawings, in which:

FIG. 1 is a schematic illustration of paper making apparatus and controls, which together incorporate the principles of the invention; and

FIGS. 2a and 2b are block diagrams of computer controllers for the paper making apparatus.

GENERAL ARRANGEMENT Referring first to FIG. 1, the depicted paper making apparatus includes a paper making machine and a paper stock supply, respectively denoted, at 10 and 12. A control system designated generally at 14 monitors, the moisture content, the mullen, and the basis weight of the paper made by the machine 10 and makes whatever corrections, if any, are required.

Considering first the paper stock supply 12, paper stock in slurry form; i.e., paper fibers and water, is provided by a suitable source, not shown, to one or more paper pulp refiners 16 arranged in parallel. These refiners 16 may be for exemplary purposes be of the type made by the Sutherland Refiner Corporation and have two confronting discs, each with bars. One of the discs is ro tated while the other is maintained stationary so that, in operation, the fibers are brushed to, in effect, shorten them. From the refiners 16 the paper stock flows into a machine stock chest 18, which serves the function of an accumulator and compensates for variations in the discharge rate from the refiners 16. The paper stock is removed from the machine stock chest 18 by a pump 20 of any appropriate type and transferred to a regulator box 22. The regulator box 22 is positioned so as to provide a relatively constant head upstream from a basis weight valve 24. The basis weight valve 24 may be of the ball type made by the Fisher Governor Company and functions to regulate the flow of the paper stock to the paper machine 10. Another pump 26 of the same general type as the pump 20 withdraws the paper stock from the regulator box 22 and then supplied it to one or more headboxes 28 forming a part of the paper machine 10.

The paper machine may be of different types as those versed in the art will appreciate. For demonstration purposes, the paper machine 10 includes an endless belt 30, such as a Fourdrinier screen, which is supported and driven by a couch roll 32 and a breast roll 34 which is adjacent to the head box 28. The couch roll is revolved by a drive motor 36 and whatever type of intermediate gearing or the like is required to drive the screen 30 at the desired speed. When operating at this speed, the paper stock in the headboxes 28-fiow through one or more onfices 38 onto the screen 30. Much of the water drains through the screen 30 after which the wet paper stock passes through a series of press rollers 40, which also can be rotated by the drive motor 36 and then proceeds to one or more dryers 42. The dryers 42 can employ any suitable type of drying medium. In this machine 10, suction and steam are used for drying purposes but some form of electric energy could be used. The dried paper next passes through calendar stacks 44 and then onto a reel 46. The dried paper in sheet form can be subsequently transported to a rewinder, not shown, for other operations.

As mentioned, the control system 14 monitors and corrects, if required, the moisture content hereinafter referred to as moisture, the mullen and the basis weight of the paper being made. This is done by a series of controllers each of which carries out the steps of measuring, computing, and correction. During the computation step any errors are calculated and these errors are converted to a form that can be subsequently utilized during the correction step when the appropriate adjustments are made. The computation step can be made by a digital computer 48 of any commercially available type capable of being programmed for carrying out the functions to be described; by way of example, an IBM 1800 Data Acquisition and Control System. The loading of the digital computer 48 can be done by a suitable control program unit 50; e.g., an IBM 1442 card read-punch unit, can be used to insert the program information into the computers memory. The selected or desired values for moisture, mullen, and basis Weight or any of the other values to be discussed can be written in by an appropriate manual entry unit 52, which can be a series of rotary decade switches or a conventional card or tape write-in device. The information relative to constants and other values used in determining errors can be entered by a parameter printer, denoted generally at 54. The parameter printer 54 can be any of the mentioned type write-in devices or a Clary printer made by the Clary Corporation of San Gabriel, Calif.

The series of controllers for carrying out the three steps are shown in FIGS. 2a and 2b and include a moisture controller 56, a mullen controller 58, a basis weight controller 60, and a speed controller 62. To avoid repetition it is now mentioned that all of the measurements for these controllers are developed in the form of analog signals which are converted to digital signals by any kind of suitable digitizer either separate from or a part of the computer 48. Also, amplifiers are shown for signal increasing and/or impedance matching purposes, if needed. All of the various digital filter and limit check sections employed by the computer 48 can employ conventional sampling multipliers, which provide the average for the number readings taken, and signal level responsive switches, which energize a warning circuit when the preset limits are exceeded and, whenever the term set point is used, it corresponds to a desired value; for instance, the basis weight set point entered in the computer 48 is the desired basis weight for the paper.

BASIS WEIGHT CONTROLLER Describing first the basis weight controller 60, which is depicted in FIG. 2a, its function is to measure the basis weight and then calculate the error, if any. Any correction is made by adjusting the basis Weight valve 24 so as to change the fiber flow; e.g., a reduction of the fiber flow would decrease the basis weight and an increase in the fiber flow would increase it.

The basis weight measurement is made by a gamma or beta ray gauge 64, shown in FIG. 1 and hereinafter referred to as a beta gauge. The beta gauge 64 is located between the calendar stacks 44 and the reel 46, but is not restricted to this location. To enable the beta gauge 64 to scan the sheet of paper between the reel 46 and the calendar stacks 44, a track at 66 is provided along which it is maneuvered by a scan mechanism depicted at 68. The beta gauge 64 has positioned on one side of the paper a radioactive source 70, which may be a radioactive isotope, such as Krypton-85, and on the other side a radiation detector 72. The beta gauge 64 may be of any commercially available type; e.g., that manufactured by Industrial Nucleonics. Similarly the scan mechanism 68 may be of any suitable type capable of being controlled by the computer 48. By way of example, the scan mechanism 68 may be energized or deenergized in any well known Way, such as by computer developed signals to a force motor which, in turn, controls a fluid pressure operated motor, so as to provide beta gauge scanning for preselected time intervals during the measurement step. I

The beta gauge 64 provides a so-called total basis weight measurement, which includes the moisture content of the paper. For determining the dry basis weight the moisture content is measured by a moisture gauge shown at 74 in FIG. 1. The moisture gauge 74 is attached to the beta gauge 64 and therefore has the same scanning movement' provided by the scan mechanism 68. The moisture gauge 74 can be any conventional kind, such as that known as Moistron made also by Industrial Nucleonics.

The basis weight controller 60 utilizes the computer 48 to calculate the basis weight error and to convert it to a form that can be used in controlling the basis weight valve 24. As shown in FIG. 2b, the computer 48 is programmed or set to perform the different computation steps designated in the different computer sections. Initially, the total basis weight and the moisture readings are taken or compiled at the scan basis weight and scan moisture sections 76 and 78, respectively, which also can provide the control for energizing and deenergizing the scan mechanism 68. The frequency of these readings is determined by any appropriate type of computer operated switches 80 and 82. These readings then are averaged and their limits checked by a pair of digital filter and limit check sections 84 and 86.

Now available at the outputs of the sections 84 and 86 are actual or measured total basis weight and actual or measured moisture signals, which are utlized in a compute dry basis weight section 88 to determine the dry basis Weight. This computation merely involves multiplymg the total basis weight by a percentage equal to one hundred percent less the percent of moisture; e.g., if the moisture is 5% and the total basis Weight 42 lbs./ 1,000 ft. then the dry basis weight will be equal to product of 95% times 42 of 39.9 lbs./ 1,000 ft. This computation at the computer section 88 provides an actual dry basis weight signal, which is compared with a dry basis weight set point at a summing junction 90.

For operator convenience the entry of the set point is made at a-manual entry section 92 of the manual entry unit 52 and the entry is made as a total basis weight to avoid requiring the operator to make the conversion to a dry basis weight. This conversion is made by the computer 48 at a computer delayed dry basis weight set point section 94. During this conversion there is, introduced at the junction 90 along with the dry basis weight set point signa a time delay signal, the purpose of which is to insure that sufficient time has elapsed after a change in the set point has been made to allow the paper stock with the new set point to reach the beta gauge 64 and the moisture gauge 74. Otherwise, over and under corrections and subsequent hunting can result. At this computer section 94 the following equation is solved:

M (k)=M (km) where M (k) is the delayed dry basis weight set point, lbs./ 1,000

M={ aa+ (X Q) ii TIT-7'11 1 1 1 1 was to nearest integer 1- =process delay time basis weight h =staleness coefiicient for basis weight loop max{-r,,}=process delay n refiner using /F C measurement i=process delay time, sec., freeness =process delay time, moisture A =process pole for freeness/mullen network, radians/ sec.

7 =staleness coefficient for overall energy determining network The constants for this equation and the subsequently discussed equations will be diiferent for each grade of paper. Also these equations determine the setting of the associated digital computer sections, which as those versed in the art will appreciate can be an analog computer. The details are conventional and will not be discussed. Also, the n refiner refers to whichever one of the refiners 16 is being considered.

After comparison at the summing junction 90', there is developed a dry basis weight error signal, which, in effect, represents the amount of correction that has to be made in the measured basis weight to achieve the basis weight set point. Because fiber flow is to be varied in order to correct the basis weight error, it is necessary to calculate a new fiber flow set point, which if met will correct the basis weight error signal. This is done at a compute new fiber fiow set point section 96. This is done in accordance with the equation:

and

D (i) is defined as 1 for i=1, N

N /T (to the lowest integer) E (k) {=present dry basis weight set pointpresent dry basis weight measurement {=error in dry basis weight M k) =present change in fiber flow set point M (k-l)=last previous change in fiber flow set point K =gain, (lbs./ 1,000 ft?) (gallons fiber/ sec.) A =process pole, radians/ sec. T =sampling interval, sec. 1 =process delay time, secs. A =loop staleness coeflicient for fiber flow A =loop staleness coefficient for basis weight (Note: Constants are unique for each grade for paper produced.)

Because variations in the speed of the screen 30 in FIG. 1 will have an influence on the measured basis weight; e.g., if the speed of the screen 30 is increased, the paper Will decrease in weight, the basis weight controller 60 also makes a speed correction, if needed. This is done by utilizing a conventional tachometer generator 98, which is a part of the speed controller 62 and is shown in FIG. 1. The tachometer generator 98 senses the speed of a part of the machine 10, such as the speed of the press rollers 40, and develops a speed signal corresponding to the speed of the screen 30 and, of course, to the speed of the paper stock as it passes between the press rollers 40. The speed of the machine 10 is read by the computer 48 at intervals determined by a computer operated switch 102 and averaged in accordance with the number of readings taken and the limits checked by a digital filter and limit check section 104. This speed signal from the section 104 is processed in a computer speed correction to fiber flow set point section 106.

To explain this speed correction with relation to fiber flow, it will be assumed that the speed is to be 1,000 ft./ min. and the fiber flow is 30 gals/min. Using a conversion factor of 8 /3 and multiplying it by 30, the 30 gals/min. is converted to 250 lbs. of fiber/min., which is equivalent to a basis weight of 250 lbs. fiber/1,000 ft. If the speed is increased and again by Way of example to 2,000 ft./ min., the basis weight would be reduced by one-half. If at this increased speed, the basis weight is to be the same, the fiber flow will have to be double. Therefore, recognizing that increases and decreases in the speed will correspondingly decrease and increase the basis weight, it will be appreciated that the fiber flow must be changed if the same basis weight is to be maintained. This speed correc tion is added to the fiber flow set point signal at a summing junction 108, to which the fiber flow set point signal is supplied at intervals determined by another computer operated timing switch 110. This provides a speed corrected fiber flow set point signal.

To properly change the fiber flow, it is necessary first to determine the actual fiber flow, which, of course, is determined by the setting or position of the basis weight valve 24. This is done by measuring the paper stock consistency and the paper stock flow. The stock consistency is the weight percentage of fiber in a slurry of fiber and water and is measured by a consistency gauge 112 positioned in FIG. 1 downstream from the machine stock chest 18. The consistency gauge 112 may be of any conventional type, such as that provided by Foxboro. The paper stock flow is measured by a flow gauge 114, which in FIG. 1, is positioned downstream from the basis weight valve 24. The fiow gauge 114 can be of many types and by way of example may be of the magnetic type made by Honeywell.

Referring again to FIG. 2b the consistency gauge output is read at a frequency determined by a computer operated timing switch 118. The readings are averaged based on the number of readings taken and their limits checked by a digital filter and limit check section 120. Similary, the stock flow gauge output is strengthened in an amplifier 122 (FIG. 1) and then read at a frequency determined by a computer operated timing switch 124 and averaged and checked for limits by a digital filter and limit check section 126. The resultant consistency and stock flow signals are used to compute the fiber flow in a compute fiber flow section 128. In this section 128 fiber flow is determined as the product of the stock flow and the consistency; for instance, if the stock flow is 3,000 gals/min. and the consistency is 3%, fiber flow will be equal to gals. fiber/min.

The fiber flow computation at the section 128 provides a fiber flow signal representing the actual fiber flow and is compared at a summing junction 130 with the corrected fiber flow set point signal to provide an error signal, which is converted by a compute basis weight valve change section 132 to a basis weight valve control signal for use in altering the position of the basis weight valve 24 in any of the usual ways; for instance, a force motor controlled fluid pressure actuated motor can be used to maneuver the control valve 24, such as that disclosed in U.S. Ser. No. 886,096 filed Dec. 18, 1969 to Chari et 211., now Pat. No. 3,634,187. The computation is in accordance with the equation:

M2 (k) K2 (E2 (k) 8 AFFTFFE2 (lo 1) K is defined as w I{FF(1 rr rr-') E (k)=error, fiber flow set point-fiber flow 'measurment K =gain of stock valve system, gal. fiber/sec. A =pole of stock valve system, radian/sec. A =loop staleness coeflicient, radian/sec. T =controller output interval, sec.

These basis weight valve control signals are applied at timed intervals determined by a computer operated timing switch 134.

In review, the basis weight controller 60 measures the total basis weight and the moisture content of the paper being made by the paper machine 10. These values are used to determine the actual dry basis weight in the computer section 88, which is then compared with the dry basis weight set point at the summing junction 90 and a dry basis weight error signal developed. This dry basis weight error signal is processed in the computer section 96 to obtain a new fiber fiow set point, which is determined by converting the dry basis weight error signal to an equivalent fiber flow quantity representing the change that has to be made in the previous fiber flow set point. Because of the influence of the speed of the machine 10 on the basis weight, the fiber fiow set point signal is corrected for speed variations at the computer section 106 and the summing junction 108. Now the corrected fiber flow set point signal is compared with an actual fiber fiow signal calculated by the computer section 128 to develop a fiber flow error signal. This fiber flow error signal them is converted to a basis weight control signal corresponding to the extent of basis valve adjustment required to correct the fiber flow and necessarily to obtain paper with the desired basis weight. This adjustment of the basis weight valve setting nulls the dry basis weight error signal.

MULLEN CONTROLLER The control of the mullen of the paper, which is its bursting strength, must consider the basis weights infiuences; for instance, heavier paper is stronger and, therefore, when the basis weight is altered, there must be a change in the mullen. The moisture content also influences the mullen. With the mullen controller 56, laboratory type measurements are made of the mullen and then adjustments are made in the energy per fiber supplied by the refiners 16. This energy per fiber determintes the freeness of the paper stock and this too is a consideration made by the mullen controller 56. For accomplishing all of this the mullen controller 56 has three loops or networks. These include a mullen determining network 136, a freeness determining network 138', and a refiner energy determining network 140 and each comprises several computer sections.

In the mullen determining network 136, there is first determined whether any correction to the mullen is required due to inaccuracies in the moisture and basis weight measured, respectively, by the moisture gauge 74 and the beta gauge 64 and due to any changes in the dry basis Weight set point. This correction is calculated in a compute mullen correction section 142 of the computer 48. The dry basis weight set point is inserted at a manual entry section 14A of the manual entry unit 52. The laboratory measurements of a paper test sample for basis weight, moisture content, and mullen are read into the computer section 142 at frequencies determined, respectively, by computer operated timing switches 146, 148 and 159. These laboratory measurements are usually inserted once per each reel of paper made, although this can be more or less frequent as determined by the application ofuthe system.

The mullen correction section 142 is set or programmed to solve the following equation:

M (k) =present corrected mullen measurement, p.s.i. MLAB=present laboratory mullen measurement, p.s.i.

8: H p.s.i. (mullen) K Constant lbs/1,000 m (dry basis wt.) BW=lab basis weight measurement, lbs./ 1,000 ft. M=lab moisture measurement, percent moisture DBWSP=dry basis weight set point, lbs./ 81,000 ft.

These mullen corrections are averaged per the number of readings taken and their limits checked in a digital filter and limit check section 152. i

In general, the mullen is more or less standardized at' a certain moisture content and basis weight. Therefore,- the output developed at the computer section 152 is a signal representing the actual mullen of the paper cor-' rected in accordance with the actual moisture content and basis weight measurements made by laboratory tests and also any changes made in the dry basis weight set point. These basis weight and moisture laboratory measurements" atford a form of calibration and thus, in effect, provide a continuing check and correction on any inaccuracies in the measurements from the moisture gauge 74 and the beta gauge 64 which are read by the basis weight controller 60'. I

This corrected actual mullen signal is compared at a summing junction 154 with the mullen set point which is inserted at a manual entry section 156 of the manual, entry unit 52 and a mullen error signal is developed cor responding to the difference. This mullen error signal is then supplied to the freeness determining network 138.

Because mullen measurements cannot be takencorp, tinuously as can be moisture and basis weight measurements, some other measurement that is closely related.

to the mullen must be used. This is the purpose. ofthe freeness determining network 138, which continuously measures the freeness of the paper stock. Freeness, which is a measure of the drainage rate of the water through the Fourdrinier screen 30 is influenced by the extent of the matting of the paper pulp fibers on the screen 30. For instance, if matting is less, the freeness is greater with a' resultant increased drainage of the water. Accordingly the basis weight of the paper will be less', as will be moisture content and, of course, the mullen. The converse happens when the matting is increased, for the freeness is less. It is therefore necessary to convert the corrected mullen error signal to a value representing the change that must be made in the freeness set point to develop a new one for correcting the error in ,the mullen of the sample tested. This is done in a compute new freeness set point section 158, which is set to solve the equation:

A =process pole for freeness and mullen determining networks radians/sec.

K =gain-p.s.i./cc. freeness This new freeness set point signal is supplied to a summing junction 160 at a frequency determined by a computer operated timing switch 162. This frequency can be once per reel or oftener, if preferred.

Because, as mentioned, the basis weight alters the mullen, there is a connection made between the basis weight controller 60 and the mullen controller 56. This connection includes a compute freeness set point correction section 164, which converts any change made in the basis weight set point entered at the manual entry-total basis weight set point section 92 to a corresponding change to be made in the new freeness set point. This freeness set point change is added as a correction at the summing junction 160 and is determined by the equation:

where dry basis wt.

01 =process gain, freeness K =gainp.s.i./cc. freeness M (k) is defined as the change in freeness set point It is next necessary to determine the actual freeness, of the paper stock. This measurement is made by a freeness measuring gauge 166 shown in FIG. 1 and positioned between the pump 26 and the machine headbox 20. The freeness measuring gauge 166 can be of any suitable type, such as the well-known Bailey Analyzer or meter. Continuous freeness measurements are made by the gauge 166 and corresponding signals are developed and then read by the computer 48 at a frequency determined by a computer operated timing switch 170. These freeness measurements are averaged and their limits checked in a digital filter and limit check section 172 after which they are compared at a summing junction 174 with the corrected new freeness set point signal so as to develop a freeness error signal representing the difference between the actual freeness measured by the freeness measuring gauge 166 and the corrected new freeness set point or the change required in the actual freeness to correct for the mullen error signal.

It should be kept in mind that freeness is determined by the extent of refining done by the refiners 16; for example, if the refining of the paper stock is increased, shorter fibers will be generated. Since there is less drainage through these shorter fibers, the freeness becomes less. The control of the extent of this refining is the function of the refiner energy determining network 140. This control is accomplished by measuring the energy input to the paper stock by the refiners 16. Consequently, the freeness error signal has to be converted to an energy set point change, which is then added to the previous energy set point so as to provide a new energy set point. This new energy set point must be met to correct for the freeness error and in turn the mullen error. This is done in a compute new energy set point change section 176. In this computer section 176 the following equation is solved:

and

N is defined as (TH-max (m))/T to the lowest integer D is defined as 1-e'* for i=1, N +1 DEF is defined as W (1 e-7 FT M =change in AT/G set point E (K =error (freeness) AF=PIOCSS pole (freeness) (see below) 7\ =loop staleness cOeflicient-freeness T =sampling interval freeness K =gain (cc. freeness)/(AT/C) r =delay time refiner i =present delay time (freeness) (see below) A and 1;- are further affected by the level of stock in the machine chest 18 which lies between the refiners 16 and the freeness measuring gauge 166. Therefore A and 1;- must be defined as follows:

' Frh Ar=Ar m 1' Q 1 E2 F TF Fr where A =initial process pole, radians/sec. A =present process pole, radians/sec. F =initia1 freeness, cc.

=present freeness, cc. h =initial chest level h=present chest level =initial delay time, secs. r =preseut delay time This equation provides the energy in terms of the pro portion between the temperature change across the refiners and the consistency of the paper stock; i.e., AT/ C.

Because of the separation of the refiners 16 and the freeness measuring gauge 166, there will be a time delay from the time an adjustment is made in the refining action of the refiners 16 and when finally sensed by the gauge 166. This delay is considered in the computation made by the computer section 1 76 and is determined by checking the level of the paper stock in the machine stock chest 18 with a level gauge 178 (FIG. 1) of any suitable kind. The output from the level gauge 178 is read at a frequency determined by a computer operated timing switch 182. These readings are averaged per the number of readings taken and their limits checked in a digital filter and limit check section 184. Also, the flow through each of the refiners 16 is measured and the total flow computed. This is done in FIG. 1 by suitable flow meters 186, which can be of the magnetic type made by Honeywell. These flow meters 186 produce outputs representing stock flow to the refiners 16 and are read by the computer 48 at a frequency established by the computer operated timing switches 190. The total flow determined by the flow meters 186 is computed at a compute total flow section 192 where total flow is determined by the equation:

where F =total refiner flowg.p.m. F =individual refiner flows-gpm. n=No. of refiners The resultant total flow signal developed by the computer section 192 is then averaged in accordance with the number of readings made and its limits checked in a digital filter and limit check section 194. The outputs from these digital filter and limit check sections 184 and 194 are fed to an input of the compute new energy set point section 176, so as to provide the time delay correction. The computer section 176 provides a corresponding signal at a frequency determined by a computer operated timing switch 196 to. two summing junctions 198 and 200. The number of these summing junctions will be equal to the number or refiners 16 used by the apparatus. As

mentioned, for simplicity purposes only two refiners 16 are shown in FIG. 1 although they may vary considerably in number in accordance with the needs of a par ticular application of the apparatus.

The refiner energy determining network 140 additionerate due to clogging or for any of the other usual reasons such as wear, or age. Therefore, at selected intervals, for instance, once per each eight hour work shift of use of the apparatus or at any other time interval, the individual refiner flows measured by the flow meters 186 are inserted into the computer 48 by way of timing switches 202. Also a sample of the paper stock from each of the refiners is tested for freenes s and these results are inserted by timing switches 204. In this way the individual operation of the refiners 16 is monitored and as will be explained ultimately adjusted. Therefore, compensation can be made for the refiners 16 that are of difierent age and sharpness and accordingly have different efficiencies. For comparison purposes, the average freeness of the paper stock from all of the refiners 16 is determined in a compute average freeness section 206. The resultant average freeness signal is then compared at summing junctions 208 and 210 with the signals representing the respective flows through the two refiners 16. This comparison results in an error signal corresponding to the diiference between the freeness of the paper stock from the associated refiner 16 and the average freeness from all of the refiners 16. H

Next, the computer 48 computes the correction to the AT/ C set point to be made for each refiner 16 in compute AT/ C set point correction sections 212 and 214. The output from the sections 212 and 214 is supplied respectively to the summing junctions 198 and 200 where, in effect,

corrections are added so that the new AT/ C set point' signal includes a correction for the differential between freeness determined by the freeness measuring gauge 166, and additionally a correction for the individual refiners contribution to the freeness; i.e., whether the freeness of the paper stock from that refiner is greater, lesser or the same as the average freeness of all the refiners 16.

The refiner energy determining network 140 has for each of the refiners 16 a summing junction 216 connected to one of the summing junctions 198 or 200. Since each operates in the same way the operation of only one will be discussed. With the summing junction 198 as the one to be considered, there will be fed to the summing junction 216 the corrected new AT/C set point signal from the junction 198 and this will be compared with the actual measured value of AT/C. To accomplish this, the consistency value is obtained from another consistency gauge 218 similar to the gauge 112' and shown in FIG. 1 upstream from the refiners 16. The temperature differential between the input and output paper stock is measured by a thermometer 222 shown positioned in FIG. 1 between the input and output of the refiners 16. The thermometer 222 may be of any suitable type; e.g., the resistance type. The thermometer 222 and the consistency gauge 218 have their outputs read by the computer 48 at a frequency determined by computer operated timingswitches 224.

This is done in the compute AT/ C section 226, where the ratio of these values is determined and then in a digital filter and limit check section 228 the average per the number of readings taken and the limits of these averages are monitored. Assuming these limits are proper the AT/C or actuator motor 240, depicted in FIG. 1. The actuator motor 240 must be of any of the usual kind capable of altering the refining operation of the refiners 16. For instance, fluid pressure operated type motors can be controlled by a conventional control signal operated force motor so as to vary the spacing of the refiner discs. The refiner control signal is determined according to the following equation:

For then? (selected one of a series of refiners) refiner energy determining networkwhere (1 -i,'r, w K,, is defined as (1 FAXET' and AT/C, F./percent wt. of fiber valve movement, sec.

A1, for ogP sa a, b, c, d, e are constants that define the interval of linearity. A B C D B are constants that represent the process gain in each interval of linearity for the n (selected one of a series of refiners) refiner.

'r =process delay time, sec., for n refiner T =control output interval, sec., n refiner A =process pole, radians/sec., nt refiner M (k) =change in valve movement, sec., for n refiner E (k)=error, (AT/C set pointAT/C measurement) N,. =1r /T the lowest integer J=max {N n=selected one of a series of refiners P =n refiner motor drive power, K

M=staleness coefiicient for the refiner energy determining network.

the process gain,

K, is defined as If because of a malfunction the AT/C value is determined to be outside the predetermined established limits by'the computer section 228, a series of control switches 230,232, 234 and 236 are actuated. During normal operation when the limits are proper, the control switches are each in their illustrated solid line positions, but when the limits are exceeded, the control switches are each moved to their broken line positions by the computer section 228. This actuation can be done by the aforementioned signal level responsive switches which in turn can cause energiza tion of the control switches. With the control switches 230, 232, 234 and 236 now all actuated so that they assume their dottedline position, the consistency of the paper stock going through the refiners 16 is still measured by the consistency gauge 218 but additionally the refiner flow is measured by the flow meter 186 and the power consumed by the refiner 16 is measured by a watt transducer 244 or any other type of instrument capable of measuring the power consumed by an electric motor in watts. Again 1t should be kept in mind that only the control of one of the refiners 16 is being described. All of these values; i.e., the flow, the consistency, and the power are read at a frequency determined by a series of computer operated switches 248 and supplied to a compute P/FC section 250. This computer section 250 is set to make the computation of the ratio between power and the product of the flow and consistency. The equivalent signal is supplied to a convert to AT/C units section 252. Then these converted AT/C signals are averaged per the number of readings and their limits checked by the digital filter and limit check section 254. Thereafter, this converted AT/C signal is compared at the summing junction 216 with the corrected new AT/C set point in the previously described Way, where an error signal is developed which by a compute output to refiner actuator section 256 is converted to a refiner actuator control signal for use in operating the refiner actuator motor 240. The computer section 256 solves the following equation:

For the n (selected one of a series of refiners) refiner energy determining network (Pi/F C) where 15. (1 Tia-MT) Kf (1 e m' converted to AT/C' units Fr O Valve movement, sec.

D 03) is defined as 1-eand the process gain,

K is defined as Pr r process delay for n refiner using, if C measurement T control output interval, sec., n refiner Pn A process pole, rad./sec., for n refiner using F measurement M 3 00) change in valve movement, see, for n refiner P actuator, 0 measurement E (k) error M is defined as IN N /T lowest positive integer J=max N N 14 P =n (selected one of a series of refiners) refiner motor drive power, KW A =staleness coefficient for the refiner energy determining network The refiner actuator motor 240 now will change the adjustment or setting of the related refiner 16 in accordance with this control signal to either increase or decrease the extent of refining so that the energy supplied by refiner per fiber corresponds to that required to correct for the error in the mullen.

To summarize the mullen determining network 136 from a laboratory test of a sample of the paper determines at the summing junction 154 the difierence between the corrected mullen of this sample and the mullen set point entered in the computer 48. This difference is the mullen error signal and is supplied to the input of the freeness determining network 138.

In the freeness determining network 138 the mullen error signal is used in the compute new freeness set point section 158 to develop the new freeness set point required to correct for the mullen error. This new freeness set point signal is corrected for any changes made in the basis weight set point in the compute freeness set point correction section 164; then is compared at the summing junction 174 with the actual freeness measurements read from the freeness measuring gauge 166. The diiference is the freeness error signal and the amount the freeness has to be adjusted to correct for the mullen error.

This freeness error signal is supplied to the refiner energy determining network where a new energy set point is calculated in AT/ C terms by the computer section 176. At the same time a correction is included in the computation to reflect the time delay which is required for a correction in the energy input by the refiner 16 to be subsequently sensed by the freeness measuring gauge 166. The refiner energy determining network 140 also checks the operation of each of the refiners 16 with a laboratory freeness measurement of the sample of the paper stock. This laboratory freeness value and the paper stock fiows through each of the refiners 16 are used to calculate in the compute average freeness section 206 the average freeness for all of the refiners 16. Then the individual freeness of each refiner 16 is compared at the junctions 208 and 210 with this average to provide the correction that must be made in the energy input from each refiner 16 and this is converted in the compute AT /C set point correction sections 212 and 214 to AT/C terms. This latter correction is included in the new AT/C 'set point signal at the summing junctions 198 and 200 so as to now provide a corrected new AT/C set point signal reflecting the amount of energy that must be supplied by each of the refiners 16 to correct for the mullen error. This AT/C set point signal is compared at the junction 216 with the actual AT/ C value to determine the extent of the difference between the actual energy being supplied by a refiner 16 with the energy required to correct for the mullen error. The AT/C error signal is then converted in a compute output to refiner actuator 238 to a refiner actuator control signal for utilization in making the adjustment of the refiner actuator motor 240 to achieve the proper refining for each refiner 16.

MOISTURE CONTROLLER The moisture controller 58 utilizes the moisture gauge 74 to measure the moisture of the paper stock during the scan by the scan mechanism 68 and then determines the difference between actual moisture content and the moisture set point. This information is used to adjust the supply of the drying medium to the dryer 42. For demonstration purposes the dryer 42 has been assumed to be steam operated; therefore, adjustment will be made in the setting of a steam valve 258, which communicates with a suitable source of steam (not shown).

The steam valve 258 may be of any conventional kind capable of varying the supply in response to an electric signal; e.g., as has been suggested a force motor controlled fluid pressure type actuator can be used. Referring to FIG. 2b the moisture set point is entered in the computer 48 at a manual entry-moisture set point section 259 of the manual entry unit 52. The moisture signals provided by the moisture gauge 74 are received at a frequency determined by a computer operated timing switch 260 by a moisture scan section 262 which in the same way as the scan moisture section 78 of the basis weight controller 60 controls the scan by the scan mechanism 68 and also takes the reading during this scan. Next, the moisture signals are averaged per the number of readings and their limits checked in a digital filter and limit check section 264. The comparison of the moisture set point with the measured moisture is made at a summing junction 266 and a moisture error signal is developed corresponding to any difference. Since steam flow is to be controlled this moisture error signal is used to calculate a new steam flow set point to correct for the mosture error signal and is done in a compute new steam flow set point section 268. In the computer section 268 the following equation is used in the computation:

N1=T22/T22 (to the lowest integer) E =error in moisture M*( k) =present change in steam flow set point M (kl)=past change in steam flow set point K =gain steam/ hr.) (percent moisture) A =process pole, radians/ sec.

T =sampling interval, secs.

-r =process delay time, secs.

A =loop staleness coeflicient for steam k =loop staleness coefiicient for moisture This new steam flow set point signal is supplied to a summing junction 270 at a frequency determined by another timing switch 272.

Next basis weight and mullen corrections must be made in the new steam flow set point if there have been or are to be changes made in either; for instance, if the basis weight is required to be increased the heavier paper will require more steam flow for drying. Of course, a heavier paper has an increased mullen, which is the reason that the mullen change also must be considered. The basis weight correction is developed by connecting the moisture controller 58 with the basis weight controller 60 at a junction 274 in the basis weight controller 60. At this junction 274 there is a corrected basis weight error signal which is supplied to a compute steam flow set point correction section 276. This computer section 276 converts the basis weight error signal to an equivalent correction to the new steam flow set point according to the following equation:

E 00) error, dry basis weight set point dry ba i measured value M K22(1 )\33TB3) (1 -ABTT33) a =gain, percent moisture/ gal. fiber/sec. N /T (to the lowest integer) K =gain, (#steam/hr.)/ (percent moisture) A =process pole, radians/ sec.

=process delay time, secs.

N /T (to the lowest integer) T =sampling interval, secs.

A =loop staleness coeiffficient for basis wt. A =loop staleness coefiicient of steam M=is defined as N +N i K is defined as r =controller output interval, secs.

T =process delay time, secs.

A =process pole for freeness and mullen determining networks, radians/sec.

A =process pole, radians/sec.

max{w }=process delay time, sec.

k =staleness COCffiCiCHt for the refiner energy determining network A =loop staleness coefiicient of steam 1 =present delay time, secs. (freeness) is defined as F =initial freeness, c.c.

F present freeness, c.c.

M"( k) =change in steam flow set point M (k) =change in freeness set point m=a positive integer This correction from the computer section 280 is inserted in the moisture controller 58 at a junction 282.

The resultant corrected new steam flow set point signal is now compared at a summing junction 284 with a signal representing the actual measured steam flow. This steam flow measurement is derived from a steam flow gauge 286 of any well-known type, such as a pressure differential measuring gauge made by Honeywell. The steam flow measurements are read by the computer 48 at a frequency determined by a computer operated timing switch 290 and then in a digital and limit check section 292 averaged per the number of readings taken and limit checked.

The steam flow error signal developed at the summing junction 284 is converted to an equivalent control signal in a compute steam valve movement section 294. This control signal is supplied to the steam valve 258 at a frequency determined by a computer operated timing switch 298 so as to effect an adjustment either for increasing or decreasing the steam flow. The adjustment changes the amount of drying provided by the dryer 242 until the moisture error signal is nulled.

Reviewing the foregoing the moisture controller 58 determines at the summing junction 266 the diiference between the actual moisture content of the paper being scanned by the moisture gauge 74 and the set point. This difference is used by the computer section 268 to calculate a new steam flow set point, which is corrected for any changes made in either or both the mullen and the basis weight. This corrected new steam flow set point is compared with the actual steam fiow and any difference is converted by the computer section 294 to an equivalent steam valve control signal. Then, the steam valve 258 is adjusted accordingly to correct for the moisture error signal.

SPEED CONTROLLER It has been explained in the description of the basis weight controller 60 that the speed of the machine will have an influence on the basis weight of the paper being made. Obviously, if the supply of paper stock from the head box 28 is kept the same and the speed increased, the machine 10 will make a paper that has a lower basis weight. The speed of the machine 10 will, of course, also have an influence on the ultimate moisture of the paper and, therefore, is a consideration in moisture control. For instance, if the moisture controller 58 determines that the moisture content is too high, then it adjusts the steam valve 258 so as to increase the steam flow to provide more drying. Additionally and without any direct connection, the speed controller 62 is employed which further compensates for too wet paper by slowing the machine speed to give more time for drying.

The speed controller 62 affords a slower response than the moisture controller 58 as will become more apparent. The speed controller 62 is connected to the steam flow gauge 286 and takes readings at a frequency determined by a computer operated timing switch 302. These readings are supplied to a compute steam flow average section 304 which is set to determine the average steam fiow over a timed interval. These average steam flow signal quantities are averaged in accordance with the number of readings taken and the limits are checked in a digital filter and limit check section 306. The steam flow aver-age signal is now compared at a summing junction 308 with an average steam flow set point signal which is inserted at a manual entry average steam flow set point section 310 of the manual entry unit 52. The error signal resulting from the comparison represents the ditference between the measured steam flow average and the average steam flow set point. This average steam flow error signal is converted to an equivalent control signal for changing the speed of the drive motor 36 in a compute speed change section 312 in accordance with the equation:

K is defined as a =process gain, percent moisture/stock fiber flow,

(gal./fiber/sec.)

K =process gain, dry basis wt./+T/sec., (speed) k =1oop staleness coefficient for moisture T =controller output interval, sec.

N is defined as Tam/T the lowest positive integer lt staleness coefficient for speed loop E (k) =error M (k)=change to variable speed actuator, sec.

These speed changes are made only periodically as determined by a computer timed switch 314, by way of example, once every ten minutes. This is much less frequently than the moisture corrections are made and accounts for its slower response. To make the speed changes the control signals in any of the customary ways alter the speed of the drive motor 36. For instance, a rheostat or the like can be adjusted by a control signal operated servo motor to vary the power input to the drive motor 36 and therefore its speed.

The advantage of utilizing this speed controller 62 with no direct connection to the moisture controller 58 can be best explained as follows. If the system provides an average steam flow at its maximum capacity; e.g., 150,000 lbs. of steam per hour, it is possible to operate, without diminishing the efficiency appreciably, at 140,000 lbs. steam per hour so as to afford an adjusting range. This 140,000 lbs. steam per hour is the average steam flow set point entered in the manual entry 310 of the speed controller 62. If it is further assumed that the moisture controller 58 determines the moisture content to be too high, the moisture controller 58 will increase the steam flow to obtain more drying. The speed controller 62 will respond by reducing the machine speed to provide more drying time. This, in effect, affords additional drying and thus enables steam flow to be reduced sooner. Then, too, the basis weight controller 60 will, as discussed, respond to this reduced speed and reduce fiber flow so that the paper cannot increase in weight. With the steam flow and the speed serving as the variables and related in this in direct way the moisture controller 58 can be operated closer to its maximum allowable moisture content or the moisture set point. This enables a higher production rate to be obtained.

OPERATIONAL SUMMARY Briefly summarizing the operation of the system, the dried paper from the machine 10 is scanned by the beta gauge 64 and the total basis weight readings are supplied to the basis weight controller 60. At the same time, the moisture gauge 74 provides the basis weight controller 60 with the moisture content readings. From this information, the controller 60 develops a dry basis weight error signal corresponding to the difierence between the actual dry basis weight of that computer from the actual moisture and basis weight readings. This signal represents the correction, if any, which must be made to provide the desired total basis Weight. Because fiber flow is the variable to be controlled, this dry basis weight error signal is used by the controller 60 to calculate a new fiber flow set point; i.e., to the fiber flow the system must be set for to correct for the basis weight error. The machine speed fluctuations are monitored by the tachometer generator 98 and converted to a fiber flow correction signal quantity, which is included in the new fiber flow set point signal. This speed correction compensates for the influence of the screens speed fluctuations on the basis weight. To determine the actual fiber flow, the consistency of the paper stock is sensed by the consistency gauge 112 and the paper stock flow is sensed by the stock flow gauge 114. These readings are used to compute the actual fiber flow and the equivalent signal is compared with the corrected fiber fiow set point signal to provide a fiber flow error signal which now represents the change that must be made in the actual fiber flow, to attain the new corrected fi-ber flow set point. This fiber flow error signal is then changed to a control signal, which is utilized to adjust the setting of the basis weight valve 24 so as to change the fiber flow until the basis weight error signal is nulled. From time to time usually at least once per each reel of paper, the mullen, moisture, and basis weight measurements of a sample of the paper made by the machine 10 are laboratory checked. The results are read into the mullen controller 56 where the mullen determining network 136 develops a mullen correction signal to compensate for any degeneration in the moisture readings from the moisture gauge 74 and the basis weight readings from the beta gauge 64. Thus, in elfect, a calibration feature is carried out by this correction. If there has been any change in the dry basis weight set point, this too is considered by the mullen controller 56. Next a comparison is made between the mullen set point and the corrected mullen so as to develop a mullen error signal representing the difierence betewen the desired mullen and the actual mullen.

Because the mullen is to be corrected by the adjustment of the operation of the refiners 16 it is first necessary to determine freeness of the paper stock and consequently the freeness determining network 138 utilizes the mullen error signal to develop a new freeness set point in signal form, which corresponds to the freeness value required to correct for the mullen error. This freeness set point signal first has a correction added to compensate for any changes that may have been previously made in the basis weight set point. Then, the new corrected freeness set point signal is compared with a freeness signal representing the actual freeness read by the freeness measuring gauge 166. Any difference results in a freeness error signal corresponding to the amount the freeness must be changed to compensate for or null the mullen error signal.

In the refiner energy determining network 140 this freeness error signal is used to develop a new energy set point, which includes the change in the previous energy set point. This new energy set point is that required to null the freeness error signal and consequently the mullen error signal. It is, of course, now necessary to determine the actual energy being applied by each refiner 16 to the pulp fiber. System lag is also considered by reading the individual refiner flows and then the total flow is computed along with the level of the paper stock in the machine stock chest 18. The resultant system lag correction is included in the determination of the new energy set point, which is developed in AT/C terms. Another laboratory check of a paper stock sample for freeness and these values along with the individual refiner flows are used to compute the average freeness of the paper stock from all of the refiners 16. The refiner energy determining network 140 compares the actual laboratory measured freeness with this average freeness to determine any difference, which is also changed to AA/C terms and included in the new energy set point. Thus, there is provided a new energy set point for the individual control of each refiner 16. Each corrected new energy set point is difierent by the amount of correction required for the associated refiner 16. This corrected new energy set point signal is compared with the actual AT/ C value in signal form for that particular refiner 16 from the computers reading, the consistency of the paper stock with the consistency gauge 218 and the temperature change with thermometers- 222. The resultant AT/ C error signal is converted to a control signal for operating the related refiner actuator motor 240 so as to adjust its refiner 16 and null the mullen error signal.

In the event there is a malfunction and the actual AT/C signal exceeds predetermined limits an alternative meas urement is employed. Hence, the consistency as read by the consistency gauge 218, the flows measured by the flow meters 186, and the power consumed by the refiners 16 as read by the Watt transducers 244 are used to calculate the P/ F C ratio for each refiner 16. This ratio is converted to AT/ C units for comparison again with the corrected new energy set point signal. The resultant error signal is converted to a control signal for supply to the associated refiner actuator motor 240.

The moisture controller 58 also reads the output from the moisture gauge 74 and compares this actual moisture content with the moisture set point so as to develop a moisture error signal if there is a difference. Because steam flow is to be the controlled variable the moisture error signal is used in calculating a new steam flow set point signal which represents what the actual steam flow must be to correct for the moisture error. The moisture controller 58 has a direct connection with both the mullen controller 56 and the basis weight controller 60; therefore, any mullen error signal or basis weight error signal is converted to the signal quantity required to correct the new steam flow set point; e.g., a heavier paper would require more steam. The actual steam flow signal quantity as measured by the steam flow gauge 286 is thereafter compared with this corrected new steam flow set point. Any error signal resulting from the difference is converted to a control signal for making the appropriate adjustment in the setting of the steam valve 258. This adjustment will provide the required steam flow for nulling the moisture error signal.

Periodically, the speed controller 62 makes changes in the speed at which the drive motor 36 operates to further facilitate moisture control. To do this the average steam fiow is read for a certain period of time. After this period of time any difference between the actual steam flow average and an average steam flow set point is determined. If there is a difierence an error signal is developed and converted to a control signal quantity for use in changing the speed of the drive motor 36.

The invention is to be limited only by the following claims.

We claim:

1. In a mullen control for apparatus of the type adapted for making paper with a desired basis weight and a desired moisture from a paper stock that has the mullen continuously measured and having a refiner for the paper stock the combination of paper mullen determining means comparing the measured mullen of the paper and a desired mullen and developing a mullen error signal quantity corresponding to the difference; paper stock freeness determining means having a certain freeness set point, the paper stock freeness means converting, in response to the mullen error signal quantity the mullen error signal quantity to an equivalent freeness and developing therefrom and from the certain freeness set point a new freeness set point signal quantity corresponding to the paper stock freeness required to obtain the desired mullen, the freeness determining means including means sensing the freeness of the paper stock and developing a freeness error signal quantity corresponding to the variations between the sensed freeness and the new freeness set point signal quantity; refiner energy determining means having a certain refiner energy set point, the refiner energy determining means converting in response to the freeness error signal quantity the freeness error signal quantity to an equivalent refiner energy and developing therefrom and from the certain refiner energy set point a new refiner energy set point signal quantity corresponding to the refiner energy to be applied to the paper stock so as to obtain the desired mullen, the refiner energy determining means including means sensing the refiner energy applied to the paper stock by the refiner and to develop a refiner energy error signal quantity corresponding to the variations between the sensed refiner energy and the new refiner energy set point signal quantity; and motor means varying the energy applied to the paper stock by the refiner in response to the refiner energy error signal quantity so as to cause the measured mullen of the paper to proximate the desired mullen.

2. A mullen control as described in claim 1, wherein the mullen determining means includes correction means having supplied thereto measured values of the basis weight and moisture of the paper being made by the apparatus and developing a corrected measured mullen in accordance with variations in the measured values from predetermined values.

3. A mullen control as described in claim 1, wherein the freeness determining means includes means correcting the new freeness net point signal quantity for changes made in the desired basis weight of the paper.

4. A mullen control as described in claim 1, wherein the refiner energy determining means includes means monitoring the flow of the paper stock and its acctnnulation in the apparatus after leaving the refiner so as to correct the new refiner energy set point signal quantity for system lag within the apparatus.

5. A mullen control as described in claim 1, wherein the refiner energy determining means further includes means periodically checking the sensed freeness With a measured freeness of the paper stock and correcting the new refiner energy set point signal quantity for differences between the sensed freeness and measured freeness.

6. A mullen control as described in claim 1, wherein the refiner energy determining means includes means sensing the temperature change in the paper stock flowing through the refiner and the consistency of the paper stock being refined thereby and developing therefrom a primary equivalent sensed refiner energy signal quantity, alternative means sensing the flow of the paper stock through the refiner, the consistency of the paper stock being refined, and the power consumed by the refiner and developing an alternative equivalent sensed refiner energy signal quantity and switch means responsive to variations in the primary equivalent sensed refiner energy signal quantity and operative when outside predetermined limits to cause the primary equivalent refiner energy signal quantity to be replaced by the alternative equivalent refiner energy signal quantity for utilization by the refiner energy determining means in developing the refiner energy error signal quantity.

7. In a mullen control apparatus of the type adapted for making paper with a desired basis weight and moisture from a paper stock that has its mullen continuously measured and having a series of refiners for the paper stock; the combination of mullen determining means comparing the corrected measured mullen of the paper and a desired mullen and developing a mullen error signal quantity corresponding to the difference; paper stock freeness determining means having a certain freeness set point, the paper stock freeness determining means converting in response to the mullen error signal quantity the mullen error signal quantity to an equivalent freeness and developing therefrom and from the certain freeness set point a new freeness set point signal quantity corresponding to the paper stock freeness required to obtain the desired mullen, the freeness determining means including means sensing the freeness of the paper stock and developing a freeness error signal quantity corresponding to the variations between the sensed freeness and the new corrected freeness set point signal quantity; and refiner energy determining means having a certain refiner energy set point, the refiner energy determining means converting in response to the freeness error signal quantity the freeness error signal quantity to an equivalent refiner energy and developing therefrom and from the certain refiner energy set point a new refiner energy set point signal quantity corresponding to the refiner energy to be applied to the paper stock so as to obtain the desired mullen, the refiner energy determining means including means periodically monitoring the measured freeness of the paper stock from each of the series of the refiners and the average of the paper stock freeness through all of the series of the refiners and means developing a freeness correction signal quantity for each of the series of refiners corresponding to the difference between the average freeness of the paper stock from all of the series of refiners and the freeness of the paper stock from the respective refiner, means developing from the freeness correction signal quantity a corrected new refiner energy set point signal quantity for each of the series of refiners, means monitoring the refiner energy supplied to the paper stock by each of the series of refiners and developing a corresponding refiner energy signal quantity, means comparing the corrected new refiner energy set point signal quantity and the refiner energy signal quantity for each of the series of refiners 22 and developing a corresponding refiner energy error signal qauntity, and motor means for each of the series of refiners each varying the energy applied to the paper stock by the respective refiner in response to the refiner energy error signal quantity so as to cause the measured mullen of the paper to proximate the desired mullen.

8. A mullen control as described in claim 7, wherein the mullen determining means includes correction means responsive to the measured values of the basis weight and the moisture of the paper being made by the apparatus and developing a corrected measured mullen in accordance with variations in the measured values from predetermined values and the freeness determining means includes means correcting the new freeness set point quantity for changes made in the desired basis weight of the paper.

9. A mullen control as described in claim 5, wherein the refiner energy determining means includes means sensing the temperature change in the paper stock flowing through the refiner and the consistency of the paper stock being refined thereby and developing therefrom a primary equivalent sense refiner energy signal quantity, alternative means sensing the fiow of the paper stock through the refiner, the consistency of the paper stock being refined, and the power being consumed by the refiner and developing an alternative equivalent sensed refiner energy signal quantity, and switch means responsive to variations in the primary equivalent sensed refiner energy signal quantity and operative when outside predetermined limits to cause the primary equivalent refiner energy signal quantity be replaced by the alternative equivalent refiner energy signal quantity for ultilization by the refiner energy determining means in developing the refiner energy error signal quantity.

10. A method of controlling the mullen of paper made by paper making apparatus of the type including a refiner for the paper stock having certain freeness and refiner energy set points corresponding to a desired paper stock freeness value and a desired refiner energy per fiber to be applied to the paper stock comprising the steps of determining the difference between a measured mullen of the paper and a desired mullen; developing from the mullen difference and from the certain freeness set point a new freeness set point representing the paper freeness required to obtain the desired mullen; determining the difference between the new freeness set point and a measured freeness value, developing from the freeness difference and from the certain refiner energy set point a new refiner energy set point corresponding to the refiner energy input to the paper stock required to obtain the desired mullen; determining the difference between the new refiner energy set point and a measured refiner energy input per paper stock fiber; and altering the operation of the refiner so that the measured refiner energy input proximates the new refiner energy set point and correspondingly the desired mullen is proximated.

11. A method of controlling the mullen of paper as described in claim 10 including the further step of correcting the measured mullen for variations in the actual basis weight and the actual moisture content of the paper being made by the apparatus.

12. A method of controlling the mullen as described in claim 10 including the further step of correcting the new refiner energy set point for system lag within the apparatus.

13. A method of controlling the mullen of paper as described in claim 10 including the further step of periodically checking the measured freeness value with a laboratory freeness measurement and when different including a compensating factor in the new refiner energy set point.

14. A method of controlling the mullen of paper as described in claim 13 and further including the step of correcting the new refiner energy set point for system lag within the apparatus.

15. A method of controlling the mullent of paper as described in claim further including the step of monitoring the limits of the measured refiner energy and when outside predetermined limits measuring in an alternative way the refiner energy input.

16. A method of controlling the mullen of paper as described in claim 10 wherein the refiner energy is measured in terms of the temperature change in the paper stock fiowing through the refiner and the paper stock consistency, checking the limits of the measured refiner energy and when outside predetermined limits, measuring the refiner energy in terms of the flow of the paper stock through the refiner, the consistency of the paper stock and the power consumed by the refiner.

17. A method of controlling the mullen of paper made by paper making apparatus of the type including aseries of refiners for the paper stock and having certain freeness and refinery energy set points corresponding to a desired paper stock freeness value and a desired refiner energy per fiber to be applied to the paper stock comprising the steps of determining the difference between a measured mullen of the paper and a desired mullen; developing from the mullen difference and from the certain fr'eeness set point a new freeness set point representing the paper freeness required to obtain the desired mullen; determining the difference between the new freeness set point and a gauge sensed freeness value; developing from the freeness difference and from the certain refiner energy set point a new refiner energy set point corresponding to the refiner energy input to the paper stock required to obtain the desired mullen; monitoring both a measured freeness of the paper stock from each of the series refiners and the average freeness from all of the series of the refiners so as to develop a freeness correction factor for each of the series of the refiners representing the difference between the average freeness and the freeness of the paper stock from a respective one of the series of the refiners; developing from the new refiner energy set point and the freeness correction factor a corrected new refiner energy set point for each of the series of refiners; measuring the refiner energy input per paper stock fiber supplied by each of the series refiners; altering the operation of each of the series of refiners in accordance with the difference between the measured refiner energy input and the corrected new refiner energy set point for the respective one of the series of refiners so that the measured refiner energy input proXimates the corrected new refiner energy set point and correspondingly the desired mullen of the paper is proximated.

18. In a moisture control for paper making apparatus having a dryer communicating with a drying medium source and having certain drying medium amount and average drying medium amount set points corresponding respectively to a desired drying medium amount and to a desired average drying medium amount for a certain time to be supplied to the dryer and a drive mechanism for moving the paper stock in the dryer relative to each other so as to dry the paper stock; the combination of moisture control means controlling the amount of drying medium supplied to the dryer so as to provide a paper with a predetermined moisture content, the moisture control means including means sensing the actual moisture content of the paper and developing a corresponding moisture signal quantity, means comparing the moisture signal quantity with a desired moisture content quantity and developing a moisture error signal quantity corresponding to the difference, means converting the moisture error signal quantity to an equivalent drying medium amount and developing therefrom and from the certain drying medium amount set point a new drying medium set point, means determining the actual mullen and the actual basis weight of the paper stock, means determining variations in the actual mullen and the actual basis weight of the paper relative to predetermined desired values, means correcting the new drying medium amount set point for the variations in the mullen and basis weight, means sensing the actual amount of the drying medium supplied to the dryer and developing a corresponding drying medium signal quantity, and means comparing the drying medium signal quantity and the new corrected drying medium set point and developing a drying medium amount error signal quantity corresponding to the difference, drying medium control means varying in response to the drying medium amount error signal quantity the amount of the drying medium supplied to the dryer so as to cause the desired moisture content to be proximated; and speed control means varying in response to variations in the amount of the drying medium supplied to the dryer relative to a predetermined amount the speed of the paper stock and the dryer relative to each other and in accordance with the variations so as to further facilitate the making of the paper with the predetermined moisture content, the speed control means including means sensing variations in the actual average drying medium amount supplied to the dryer for a certain period of time from the average drying medium amount set point to develop a speed control signal corresponding to the variations, means varying in response to the speed control signal the relative speed of the dryer and paper stock, and basis weight control means for controlling the paper stock flow to the apparatus so as to provide the paper with certain basis weight, the basis weight control means including means sensing the variations in the speed of the paper stock and the dryer relative to each other and altering the paper stock flow in accordance with the variations in the speed made by the speed control means.

19. In a moisture control for paper making apparatus having a dryer communicating with a drying medium source and having a certain drying medium amount set point corresponding to a desired drying amount a drive mechanism for moving paper stock relative to the dryer so as to dry the paper stock, the combination of means sensing the moisture content of the paper and developing a corresponding moisture signal quantity, means comparing the difference between the moisture signal quantity and a reference quantity corresponding to the desired moisture content of the paper and developing a moisture error signal corresponding to the difference, means converting the error signal quantity to an equivalent drying medium and developing therefrom and from the certain drying medium set point a new drying medium amount set point, means determining the actual mullen and the actual basis weight of the paper stock, means determining variations in the actual mullen and the actual basis weight of the paper stock from predetermined desired values, means correcting the new drying medium amount set point for the variations in the mullen and the basis weight, means sensing the actual amount of the drying medium supplied to the dryer and developing a corresponding drying medium signal quantity, means comparing the drying medium signal quantity and the corrected new drying medium amount set point and developing a drying medium amount error signal quantity corresponding to the difference, and a drying medium control varying in response to the drying medium amount error signal quantity the amount of the drying medium supplied to the dryer so as to substantially null the moisture error signal quantity.

20. A method of controlling the moisture content of paper made with paper making apparatus of the kind including a dryer communicating with a drying medium source and having a certain drying medium amount set point corresponding to the desired amount of the drying medium to be supplied to the dryer and a drive mechanism for moving the paper stock and the dryer relative to each other comprising the steps of determing the difference between the actual moisture content of the paper and a desired moisture content developing from the moisture difference and the certain drying medium amount set point a new drying medium amount set point representing the amount of the drying medium to be supplied to the dryer to obtain the desired moisture content, determining the difference between the actual amount of the drying medium supplied to the dryer and'the new drying medium amount set point, varying the amount of the drying medium supplied to the dryer in accordance with the difference, determining the difference between the average amount of the drying medium supplied to the dryer for a certain time and a desired average amount and varying the relative speed of the dryer and the paper stock in accordance with the difference to further facilitate obtaining the desired moisture content, measuring variations in the basis weight and the mullen of the paper relative to predetermined values, and correcting the new drying medium amount set point for the measured variations in the basis weight and the mullen of the paper relative to the predetermined values.

21. In a control system for paper making apparatus of the type having a refiner for the paper stock, a dryer communicating with a drying medium source, and a drive mechanism for moving the paper stock in the dryer relative to each other so as to dry the paper stock; the combination of basis weight controller means including means including means sensing the actual basis weight of the paper and determining the difference between the actual basis weight of the paper and a desired basis weight and in accordance with the difference varying the paper stock flow so as to provide paper with a desired basis weight and means sensing variations in the relative movement between the paper stock and the dryer with respect to a certain reference and correcting the paper stock flow in accordance with variations in the relative movement; mullen controller means having supplied thereto a measured mullen of the paper and determining the difference between the measured mullen of the paper and a desired mullen and in accordance with the difference varying the refiner energy per fiber supplied by the refiner so as to provide paper with the desired mullen; moisture controller means including means sensing the actual moisture content of the paper and determining the difference between the actual moisture content of the paper and a desired moisture content and in accordance with the difference varying the amount of the drying medium supplied to the dryer and correction means responsive to the difference between the actual mullen and the desired mullen and to the difference between the actual basis weight and the desired basis weight and in accordance therewith correcting the desired moisture content; the mullen controller means also including means providing measured values of the basis weight and the moisture content of the paper stock being made by the apparatus and correction means responsive to the measured values of the basis weight and the moisture content and developing therefrom a corrected measured mullen in accordance with the variations in the measured values from predetermined values.

22. A control system as described in claim 21 and further including speed controller means sensing the actual average amount of the drying medium supplied to the dryer for a predetermined time, and determining the difference between the actual average amount of the drying medium and a desired average amount and in accordance with the difference varying the relative speedof the paper and dryer.

23. A control system as described in claim 21, wherein the moisture controller means includes means sensing the actual moisture content of the paper and developing a corresponding moisture signal quantity, means comparing the moisture signal quantity with a desired moisture content and developing a moisture error signal quantity corresponding to the difference, means converting the moisture error signal quantity to an equivalent drying medium amount and developing therefrom and from a certain drying medium amount set point a new drying medium set point representing the drying medium amount required to obtain the desired moisture content, means sensing the actual amount of the drying medium supplied to the dryer and developing a corresponding drying medium signal quantity, means comparing the drying medium signal quantity and the new drying medium set point and developing a drying medium amount error signal quantity corresponding to the difference, and drying medium control means varying in response to the drying medium amount error signal quantity the amount of the drying medium supplied to the dryer so as to cause the desired moisture content to be proximated.

24. A control system as described in claim 21, wherein the mullen controller means includes mullen determining means comparing the measured mullen of the paper and the desired mullen and developing a mullen error signal quantity corresponding to the difference; paper stock freeness determining means having a certain freeness set point and converting in response to the mullen error signal quantity the mullen error signal quantity to an equivalent freeness and developing therefrom and from the certain freeness set point a new freeness set point signal quantity corresponding to the pape stock freeness required to obtain the desired mullen, the freeness determining means also sensing the freeness of the paper stock and developing a freeness error signal quantity corresponding to the variations between the sensed freeness and the new freeness set point signal quantity; refiner energy determining means having a certain refiner energy set point and converting in response to the freeness error signal the freeness error signal quantity to an equivalent refiner energy and developing therefrom and from the certain refiner energy set point a new refiner energy set point corresponding to the refiner energy to be applied to the paper stock so as to obtain the desired mullen, the refiner determining means also sensing the refiner energy applied to the paper stock by the refiner and developing a refiner energy error signal quantity corresponding to the variations between the sensed refiner energy and the new refiner energy set point signal quantity, and motor means varying the energy applied to the paper stock by the refiner in response to the refiner energy error signal quantity so as to cause the measured mullen of the paper to proximatethe desired mullen.

25. A control system as described in claim 24, wherein the refiner energy determining means includes means sensing the temperature change in the paper stock flowing through the refiner and the consistency of the paper stock being refined thereby and developing therefrom a primary equivalent'sensed refiner enery signal quantity, alternative means sensing the flow of the paper stock through the refiner, the consistency of the paper stock being refined, and the power being consumed by the refiner and developing therefrom, an alterative equivalet sensed refiner energy signal quantity, and switch means responsive to variations in the primary equivalent sensed refiner energy signal quantity and replacing when outside predetermined limits the primary equivalent energy signal'quantity with the alternative equivalent refiner energy signal quantity for the utilization by the refiner energy determining means in developing the refiner energy error signal quantity.

26. A control system as described in claim 24, wherein the moisture control means includes means sensing the actual moisture content of the paper and developing a corresponding moisture signal quantity, means comparing the moisture signal quantity with a desired moisture content quantity and developing a moisture error signal quantity corresponding to the difference, means converting the moisture error signal quantity to an equivalent drying medium amount and developing therefrom and from the certain drying medium amount set point a new drying medium set point, representing the drying medium amount required to obtain the desired moisture content, means sensing the actual amount of the drying medium supplied to the dryer and developing a corresponding drying medium signal quantity, means comparing the drying medium signal quantity and the new drying medium set point and developing a drying medium amount error signal quantity corresponding to the difierence, and drying medium control means varying in response to a drying medium amount error signal quantity the amount of the drying medium supplied to the dryer so as to cause the desired moisture content to be proximated.

27. A control system as described in claim 26 and further including speed controller means determining the difference between the actual average amount of the drying medium supplied to the dryer for predetermined time and a desired average amount and in accordance with the difference varying the relative speed of the paper and the dryer and wherein the basis weight controller means alters in response to the relative speed of the paper stock and the dryer the paper stock flow to compensate for variations in the relative speed on the basis weight.

28. A method of controlling the moisture content, mullen and basis weight of paper made by paper making apparatus of the type having a refiner for the paper stock, a dryer communicating with a drying medium source, and a drive mechanism for moving the paper stock and the dryer relative to each other so as to dry the paper stock comprising the steps of determining the actual basis weight of the paper stock, determining the difference between the actual paper stock flow in accordance with the difierence so as to obtain the desired basis weight measuring the mullen of the paper stock, measuring the basis weight and the moisture content of the paper stock being made by the paper making apparatus correcting the measured mullen for variations in the measured basis weight and the measured moisture content relative to the predetermined values as to obtain the desired basis weight determining the actual relative movement between the paper stock and the dryer, correcting the new paper stock flow set point for variations in the actual relative movement between the paper stock and the dryer relative to a desired value, determining the difference between the measured mullen of the paper and a desired mullen, developing from the mullen difference and from a certain freeness set point representing a desired freeness a new freeness set point representing the paper stock freeness required to obtain the desired mullen, determining the actual freeness value of the paper stock, determining the diiference between the new freeness set point and the actual freeness value; developing from the freeness difference and from a certain refiner energy set point representing desired refiner energy per fiber to be applied by the refiner to the paper stock a new refiner energy set point corresponding to the refiner energy input to the paper stock required to obtain the desired mullen, determining the actual refiner energy input per paper stock fiber, determining the difference between the new refiner energy set point and the actual refiner energy input per paper stock filter, altering the operating of the refiner so that the measured refiner energy input proximates the new refiner energy set point and correspondingly the desired mullen is proximated, determining the actual moisture content of the paper, determining the difference between the actual moisture content of the paper and a desired moisture content, developing from the moisture diiference and from a certain drying medium amount set point representing a desired drying medium amount a new drying medium amount set point corresponding to the drying medium amount to be supplied to the dryer to obtain the desired moisture content, determined the actual amount of the drying medium supplied to the dryer, correcting the new drying medium amount set point for variations in the actual basis weight and the actual mullen of the paper relative to the desired values, determining the difference between the actual amount of the drying medium supplied to the dryer and the new drying medium amount set point and varying the amount of the drying medium supplied to the dryer in accordance with the difference.

29. A method as described in claim 28 and including determining the average amount of the drying medium supplied to the dryer for a predetermined time, determining the diiference between the average amount of the drying medium supplied to the dryer for the predetermined time and a desired average amount and varying the relative speed of the paper stock and the dryer in accordance with the difference to further facilitate obtaining a paper with the desired moisture content.

30. A method as described in claim 28 further including monitoring the limits of the measured refiner energy and when outside predetermined limits measuring in an alternative way the refiner energy input.

31. A method as described in claim 28 and including the further step of periodically checking the measured freeness value with a laboratory freeness measurement and when different including a compensating factor in the new refiner energy set point.

32. A method as described in claim 28 wherein the apparatus has a series of refiners and further including the steps of monitoring both the freeness of the paper stock from each of the refiners and the average freeness from all of the series of refiners so as to develop a freeness correction factor for each of the series of refiners, developing from the difference between the average freeness and the freeness of each of the series of refiners a corrected new refiner energy set point for each of the series refiners, determining the difference between the measured refiner energy input per paper stock fiber supplied by each of the series of refiners and the corrected new refined energy set point for the respective refiner and altering the operation of the respective in accordance with the difference so that the corrected new refiner energy set point is proximated.

33. A method as described in claim 32 including correcting the new drying medium set point for measured variations in the basis weight and the mullen of the paper, monitoring the limits of the measured refiner energy and when outside predetermined limits measuring in an alternative way the refiner energy input, correcting the measured mullen for variations in the actual basis weight and the actual moisture content of the paper being made by the apparatus, and periodically checking the measured freeness value with a laboratory freeness measurement and when different including a compensating factor in the new refiner energy set point.

34. A method of controlling moisture content, mullen and basis Weight of paper made by paper making apparatus of the type having a refiner for the paper stock, a dryer communicating with a drying medium source and a dryer mechanism for moving the paper stock and the dryer relative to each other so as to dry the paper stock comprising the steps of determining the actual basis weight of the paper stock; controlling the paper stock flow in accordance with the difiierence between the actual basis weight and a desired basis weight; varying paper stock flow as the relative speed of the paper stock and the dryer are varied to correct for the influence of speed variations on the basis weight; determining the actual mullen of the paper stock; determining the difference between the actual mullen and a mullen of the paper; developing from the mullen diiference and a certain refiner energy set point representing a desired amount of refiner energy per fiber to be supplied by the refiner a new refiner energy per fiber set point; determining the actual refiner energy per fiber supplied by the refiner; comparing the actual refiner energy per fiber supplied by the refiner with the new refiner energy per fiber supplied by the refiner with the new refiner energy per fiber set point to develop a diiference; and controlling the operation of the refiner in accordance with the difierence so as to proximate the desired mullen; determining the actual moisture content of the paper stock; and controlling the amount of the drying medium supplied to the dryer in accordance with the difierence between the actual moisture content of the paper and a desired moisture content.

Carroll, Computer Control, Paper Trade Journal (Sept. References Cite 10, 1962), vol. 146 #37, pp. 42-5. UNITED STATES PATENTS Casey, Pulp and Paper, Inte'rscience Publishers (1961),

vol. I, p. 310; vol. 3, pp. 1297, 1333, 1446. 2:3 5 Dipre, New Eng. Closed Loop Control of B. W., Tappi 3,260,642 7/1966 CamerI frT IIIIII 162-252 (Nmmber 1963) 46 USA4811- Hart et a1 X S. i y Exalninel. FOREIGN PATENTS A. DANDREA, JR, Assistant Examiner 705,626 3/ 1965 Canada 162-253 10 US. Cl. X.R.

OTHER REFERENCES Betts, Automation in the Paper Industry, Paper Maker (January 1969) Pp. 50-5. 

